How do I create multiple UV maps for use in UE4?
OK so my original assumption was incorrect. I was trying to set the mesh up so I could apply two (or more) different materials to the static mesh in UE4. I thought that I would need to create two UV maps and then somehow use those in UE4, but the answer is much simpler:


Go to Edit mode for your object in Blender
Unwrap the mesh
Add additional material slots using the '+' button
Highlight the faces on your mesh that you want assigned to this material channel and then click Assign




Do this for all faces in the mesh, assigning each face to a material slot.


Export the fbx file and import into UE4.
In UE4 you will see additional material slots allocated to your static mesh. You can then drag and drop materials from your UE4 library onto the mesh.




Additional tips:


I left the texture channels blank in Blender for each material slot as I was going to use materials (that already have textures assigned to them) that already resided in UE4. If you were to assign a texture to the material slot in Blender then that texture would be exported to UE4 inside the fbx file and appear alongside your mesh object in the Content Browser.
If a face appears missing on your mesh, it is likely that the face normal has been flipped during editing. Go back into edit mode in Blender, highlight the problem face, CTRL + F to bring up the Face menu, and Flip Normal. Re-export the fbx, right click the asset in UE4 and Re-import.




You can also display all face normals in edit mode by clicking Display Face Normals in the Mesh Display pane:



Hope this helps someone in the future.